Salen impregnated silica gel as a new sorbent for on-line preconcentration of cadmium(II)

A new sorbent – salen impregnated silica gel – was prepared and characterised for application as a minicolumn packing for flow-injection on-line preconcentration of cadmium(II). The system was coupled with flame atomic absorption spectrometer (FI-FAAS). The optimal pH for Cd(II) sorption was in the range of 7.4–8.8 and nitric acid (1%, v/v) was efficient as eluent. Sorption was most effective within the sample flow rate up to 7?mL?min^?1. Sorption capacity of the sorbent found in a batch procedure was 26.3?µmol?g^?1 (2.95?mg?g^?1). Enrichment factor (EF) and limit of detection (LOD) obtained for 120-second loading time were 113 and 0.26?µg?L^?1, respectively. The sorbent stability in the working conditions was proved for at least 100 preconcentration cycles. The evaluated method was applied to Cd(II) determination in various water samples.     

New Recoverable Organoselenium Catalyst for Hydroperoxide Oxidation of Organic Substrates

New benzisoselenazol-3(2H)-one covalently bounded to a silica support was synthesized and characterized. It was used as an effective, selective, and easy-to-regenerate catalyst for t-BuOOH and H₂O₂ oxidation of alkyl arenes to alkyl aryl ketones, aromatic aldehydes to arene carboxylic acids, and sulfoxides and/or sulfones.     

Novel Chromogenic 21-Membered Azocrown Ether Lithium Selective Reagent

Abstract

Novel chromogenic 21-membered crown ether having an intraannular azo and hydroxy subunits has been used as a complexing reagent for alkali metal cations. The complex formation was detected by visible spectroscopy and formation constants were calculated. The most pronounced spectral changes were observed for lithium ion.     

In situ photoexcitation of silver-doped titania nanopowders for activity against bacteria and yeasts

Photocatalytic and in situ microbial activity of the amorphous and annealed states of Ag-doped and un-doped titania were examined. Studies on their structure, morphology, composition, and the photo-absorption characteristics of these materials were performed. These results were correlated with the photocatalytic and microbial activity against methicillin resistant Staphylococcus aureus K324 (MRSA), methicillin susceptible S. aureus ATCC 25923 (MSSA), Escherichia coli PA 170, and yeasts Candida albicans ATCC 90028. The annealed powders containing anatase form of titania exhibited relatively higher photocatalytic activity,corresponding to activity against MRSA,when exposed to UV-A radiation. In comparison, amorphous powders exhibited low photoactivity and showed poor antibacterial performance against MRSA under UV-A exposure. Doping of amorphous titania with Ag resulted in an anti-MRSA effect without exposure to UV radiation. In the Ag-doped crystalline anatase samples, the size of Ag primary nanocrystallites increased, which led to the decrease in the surface concentration of Ag and detriment anti-MRSA activity.     

Routes of π-electron delocalization in 4-substituted-1,2-benzoquinones

The substituent effect in 4-substituted-1,2-benzoquinone is investigated by means of modeling using B3LYP hybrid functional in conjunction with the 6-311+G(d,p) basis set. The interrelation between different types of substituents, X = NO, NO(2), CN, CHO, H, Me, OMe, OH, NH(2), NHMe and N(Me)(2), and both CO groups has been characterized both qualitatively and then quantitatively by means of several measures of π-electron delocalization (HOMA, MCI, DI, FLU) based on structural and electronic properties of 4-substituted-1,2-benzoquinones chosen for analysis. Results of this analysis clearly show that only the meta-placed CO group is affected by substituents, whereas the para-placed CO group is rather insensitive to substitution. These observations may help to explain diversified chemical properties (including reactivity) of CO centers in o-benzoquinone derivatives. Among others, they may explain differences in proton-accepting properties of carbonyl O atoms, as it is shown for simple models in which carbonyl groups in o-benzoquinone act as proton acceptors in H-bonds of O···H-F type.     

Stimulation of Lignan Production in Schisandra rubriflora In Vitro Cultures by Elicitation

The study investigated the effect of elicitation with: chitosan (CH) (200 mg/L), yeast extract (YeE) (3000 mg/L), ethephon (ETH) (25 µM/L), and methyl jasmonate (MeJA) (50 µM/L), on lignan accumulation in agitated and bioreactor (Plantform temporary immersion systems) microshoot cultures of female (F) and male (M) Schisandra rubriflora Rehd. et Wils. (Schisandraceae) lines. The elicitors were supplemented on the 10th day of culture. Biomasses were collected at 24 h and 48 h, and 4, 6, and 8 days after the addition of each elicitor. The 24 compounds from the dibenzocyclooctadiene, aryltetralin, dibenzylbutane, and tetrahydrofuran lignans and neolignans were determined qualitatively and quantitatively in biomass extracts using the UHPLC–MS/MS method. The highest total contents [mg/100 g DW] of lignans were: for CH-95.00 (F, day 6) and 323.30 (M, 48 h); for YeE 104.30 (F, day 8) and 353.17 (M, day 4); for ETH 124.50 (F, 48 h) and 334.90 (M, day 4); and for MeJA 89.70 (F, 48 h) and 368.50 (M, 24 h). In the biomass extracts of M cultures grown in bioreactors, the highest total lignan content was obtained after MeJA elicitation (153.20 mg/100 g DW). The maximum total lignan contents in the biomass extracts from agitated and bioreactor cultures were 3.29 and 1.13 times higher, respectively, than in the extracts from the non-elicited cultures. The poor understanding of the chemical composition and the lack of studies in the field of plant biotechnology of S. rubriflora emphasize the innovativeness of the research.     

Energetic and geometric characteristics of the substituents. Part 1. The case of NO2 and NH2 groups in their mono-substituted derivatives of simple benzenoid hydrocarbons

Structural Chemistry - Simple polycyclic aromatic hydrocarbons, substituted by strongly electron-donating (NH2) and withdrawing (NO2) groups, are studied employing density functional theory (DFT)...